It's very hard to properly lead into a review of The Sims 3, so I think I'll settle for this: I spent the last week and a half more concerned with how well-rested my Sim family was than how much sleep I was getting myself.
The latest iteration in the franchise that distills the concept of games like SimCity and SimTower down to its most basic concept, Sims 3 places you, the player, in charge of a virtual person, or family, or couple, or whatever. More than just minions, your Sims are... well, they're like pets. You need to see to their needs, you need to help them become successful, and unless you're the sadistic sort who traps them in a room with no toilet and no doors, you need to keep them happy.
When you start Sims 3, you can jump right into the town of Sunset Valley with any of a dozen or so pre-existing Sim families (or people, or couples, etc.). They have houses, they have friends and relationships, and they already have jobs and goals: One I played was a young doctor already working her way up the medical ladder with a dream of being a world-class surgeon.
Creating your own, on the other hand, can be far more engaging. The Sim builder is fairly complex, and it's easy to lose hours getting your virtual family to look just how you want them. Beyond their appearances, though, every Sim has a handful of traits that make up their personality: Your Sim might be charismatic, they might be flirty, they might have no sense of humor, they might be obsessively neat, they might be total slobs, etc.
Beyond affecting what sort of things your Sim can do (Natural Cooks skill up in making food more quickly, Bookworms finish their school work faster,) their traits also affect their dreams and desires. Dreams come in two varieties - normal, everyday, mundane dreams, and lifelong goals. For the former, your Sim might want to read a book, or kiss their girlfriend, or cook a meal. For the latter, you might have an aspiring Leader of the Free World or genius scientist on your hands - hell, one of my Sims (who was Afraid of Commitment) wanted to break as many hearts as possible in her lifetime.
Both Traits and their goals contribute to their overall Mood, and it's very clear what makes your Sims happy or unhappy (which, thankfully, makes it easy to correct). Your Slob of a Sim could be perfectly fine in a room, but when your Neat Sim starts freaking out about being in the same room as some old spoiled food, you know it's time to do the dishes.
The Sim experience is greatly enhanced by the concept of the "Living Town." In previous Sims games, your family was largely limited to their own residence (or dorm, or vacation home). Sure, they'd go off to work, or maybe over to friends' houses, but for the most part you could only control them in their immediate neighborhood. Not so in Sims 3 - the entire town of Sunset Valley is navigable, and you can spend just as much time watching random villagers play chess in the town park as you can managing your own household.